A device of the type to which the invention relates may comprise a working cylinder with an oil filled working chamber having a working piston borne slidably therein, the piston including damping means such as valves, and carried at the end of a hollow piston rod that passes sealingly out of the working cylinder. A gas cushion disposed in a gas spring chamber connected with the working chamber puts the oil in the working chamber under pressure. An oil reservoir chamber defined by an outer jacket tube, preferably surrounding the working chamber, contains oil and gas, with a free surface therebetween. A hollow pump rod is elastically borne on a partition, which pump rod is communicated at one end with the oil reservoir chamber below its oil surface, and at its other end, which has a pump suction valve, it cooperates with a pump chamber disposed in the hollow piston rod for regulation of the level in that, as a function of the back and forth spring motions, it delivers oil from the oil reservoir chamber into the working chamber, while upon exceeding of the ideal level, oil can flow from the working chamber into the oil reservoir through a control opening provided in the pump rod. A pump outlet valve disposed at the end of the pump chamber remote from the partition, and located in a control sleeve that is located in the piston rod cavity between the piston rod and the pump rod, forms, with the piston rod, passages from the pump outlet valve to the working chamber. The end of the control sleeve toward the partition preferably constitutes a control edge for the control opening. In the gas spring chamber in the region of the surface between oil and gas, there is movably disposed a separating body of solid material.
From German Patent No. 1,630,107, a shock absorbing device similar to the above described telescopic spring damping element with internal level regulation is known. In this known device, however, the separating body between oil and gas located in the gas spring chamber is made as a separating membrane. In such a structure, diffusion of the media that are to be separated from each other may have an unfavorable effect on the functioning of the level regulating spring damper element. Additionally, in this known spring damping element, the pump rod elastic suspension, provided to avoid a disadvantageous rectangular pump diagram, is so constituted that the pump rod end that is to be suspended is made as a rubber/metallic part borne in a special chamber provided in the partition. This is not only technically cumbersome, but it also involves a rather axially long construction of the spring damping element. Still further, mounting of the known level regulating, spring damping element with an upwardly disposed piston rod is generally not possible. Also, the pump outlet valve is disposed in the region of the working piston, and thus because of the gas in the oil reservoir chamber there would remain a gas cushion in the pump chamber that would practically hinder a further pumping of oil.
In a spring damping element of the type disclosed in German Patent No. 2,519,922, it is true that incorporation in a vehicle with an upwardly disposed piston rod is possible. However, in this known spring damping element the separating body of solid material for separation of oil and gas in the gas spring chamber is constituted by a stepped sleeve arrangement that is specially wound, surrounding the work cylinder, with respective annular passages, the upper one for gas being especially narrow, and the lower for the passage of oil, whereby the two passages are connected with the working chamber at their ends that are opposed to each other. Here there is not only a great outlay for construction, but because of this separating sleeve arrangement and the passages, this known spring damping device again does not function if incorporated in a vehicle with the piston rod at the bottom. Moreover, in this known spring damping element the fixing of the control sleeve in the piston rod cavity in the region of the working piston is effected by a special technically expensive bearing arrangement. In addition, in this known spring damping element, the elastic bearing of the pump rod that is not shown in detail is made according to the known pump rod bearing of German Patent No. 1,630,107.
As will be clear, in the spring damper element according to German Patent No. 2,519,922, especially because of the sleeve arrangement for separation of gas and oil, the bearing of the control sleeve disposed in the piston rod cavity and the elastic suspension of the pump rod, even apart from the considerable technical outlay, there is also an axially longer construction, i.e., a greater fixation length of the spring damping element. This as well as other drawbacks in the known spring damping element with internal level regulation make it not well suited for large scale manufacture. Moreover, there is only a limited applicability of the known spring damping element with internal level regulation because of the many configurations of present day axle arrangements in cars, combination vehicles and truck construction, in view of the actually present space for incorporation for an element or device of the kind in question, to bring about the different transmission ratios of the linkages, as well as the necessity of producing a multiplicity of intrinsic vibration values.
A basic problem to which the instant invention is directed is the production of a simple and efficient self pumping, hydropneumatic, telescopic, spring damping element with internal level regulation that avoids the drawbacks of the known damping elements and is simpler in construction, which has a shorter axial fixation length, and which can be mounted in various positions and orientations, so that its manufacture in large series will be economically feasible. Therefore, the spring damping element that is to be produced in accordance with the invention will be applicable in many ways to modern requirements in automobile construction.
This problem is generally solved in accordance with the invention in that, in the case of a telescopic, spring damping element with internal level regulation of the type in question, in that the gas spring chamber contains, in a known way, a separating piston guided with seal at its periphery, that in the region of the partition that supports or braces the pump rod the gas spring chamber is connected axially to the working chamber and is communicated with it via at least one passage opening in the partition, wherein the partition itself in the region of the working chamber is elastic and presents a pump suction tube for connection of the pump rod cavity with the oil reservoir below the surface of the oil, which tube is made to be yieldable with respect to the movements of the partition, and the separating piston on its face toward the partition presents a recess in which the pump suction tube can be received upon location of the separating piston in the region of the partition.
A spring damping element with internal level regulation according to the invention is technically more simple in construction and basically is shorter in the hydraulic part also, relative to known damping devices of the type in question. Because of its overall construction, it is ensured that whether incorporated with the piston rod below or above, there is no residual gas cushion occurring in the pump chamber, whereby incorporation that is independent of orientation or position is made possible for this telescopic spring damping element in accordance with the invention. Thereby the spring damping element of the invention can be utilized in many ways. Because of the technical simplicity and compactness, as well as the capability of assembly that is independent of position or orientation, the economical production of the level regulating, spring damping element on a large industrial scale is readily attainable.
From German Patent No. 1,254,031, especially FIG. 2, it is known in principle, of course, that a gas spring chamber that has a separating piston sealingly guided at its periphery can be connected axially to a working chamber in the region of a partition that supports or braces the pump rod, whereby the gas spring chamber is communicated with the working chamber via a passage opening in the partition. However, this known arrangement has a substantially different construction otherwise relative to the level regulating, telescopic, spring damping element in accordance with the invention. Thus, in the known arrangement, the partition is made rigid, and also the work piston that is slidably guided in the work chamber has no damping valves or devices. This disclosure in the literature therefore would not contribute to the present invention.
According to an especially preferred form of embodiment of the invention, the partition in the region of the work chamber is made as a leaf spring wall, and the pump suction tube is made as a tube spiral perpendicular to the axis of the damper, between its fastenings to the partition on the one hand and to the oil reservoir on the other. Hereby, there is an especially simple compact construction.
There is obtained a simplified construction also if the two fastenings of the pump suction tube are made as sealed plug connections.
It is also advantageous to make the fastening of the control sleeve in the piston rod cavity as a sealed plug connection, whereby the end of the control sleeve turned away from the partition presents a peripheral seal against the piston rod cavity, outside the pump outlet valve, and is applied frontally against the adjacent front wall of the piston rod cavity, which there presents a venting opening at the end.
In the interest of simplified manufacture, the fastening of the region of the partition in the jacket tube that closes off the oil reservoir is advantageously made as a sealed plug connection. Correspondingly, the fastening of at least one of the two closures at the ends (cover and floor) of the damping device is advantageously made in the jacket tube as a sealed plug connection.
The advantages of the invention are especially evident if, according to a further feature of the telescopic spring damping element, it is made as a modular system wherein the work cylinder that contains the working chamber and appurtenant modules, especially the working piston with vacuum and pressure damping valve means, piston rod with pump chamber, control sleeve with pump discharge valve, pump rod with pump suction valve, piston rod guide and sealing complex, is made as a uniform standard module, and the rest of the function modules, especially the oil reservoir, gas spring chamber with separating piston, etc., are made as modules that are varied according to the application in question as to size and/or spacial arrangement. Thereby the gas spring chamber with the separating piston can at least partly surround the oil reservoir or the working cylinder. Also, the gas spring chamber with the separating piston and/or the oil reservoir chamber can be modules disposed separately with reference to the standard module group, and joined with the work chamber by respective tube conduits.
The features of such a modular system according to the invention, offering simplicity, compactness and assembly that is independent of position, make possible a practically unrestricted application of the spring damping element in automobile construction. Particularly, with this further feature of the invention, there is an extremely good capability of adaptation of the spring damping element to the available space for incorporation in the vehicle in question. Moreover, such a shock absorber element according to the invention is variable in spring characteristic design, with consideration of fixed transmission ratios (wheel path to strut path) of the axle/strut linkages. No additional detailed explanation is necessary to establish that with such a modular system there is also a simple and economical manufacture on an industrial scale of the level regulating shock absorber.
For the sake of good order, let it be said that the length of the pump suction tube dipping into the oil reservoir is to be selected to correspond to the particular application in question. This means that this immersing length is maximal with assembly of the spring shock absorber element with piston rod disposed below, and minimal when the piston rod is disposed upward.
Other aspects, features and advantages of the invention will be apparent from the ensuing description of preferred exemplary embodiments, taken with reference to the accompanying drawings and their schematic illustrations of exemplary preferred embodiments.